function sendMessage(route) {
  const travelTime = route.reduce((acc, cur) => acc + cur, 0)/3e5;
  const delayTime = 0.5 * (route.length - 1);
  return (travelTime + delayTime).toFixed(4);
}


let output = sendMessage([300000, 300000]);
output = sendMessage([384400, 384400]);
output = sendMessage([1000000, 500000000, 1000000]);
console.log(output);